The invention relates to a ring for ring spinning and ring twisting machines.
A ring for a ring spinning or ring twisting machine must not only have a precision-machined shape, but also an optimized surface adapted to the requirements, in order to allow a ring traveler rotating on the ring at speeds of up to 55 m/s to run smoothly and with as little wear as possible. For this purpose, the surface of the ring must be as smooth and as hard as possible and should oppose only slight running resistance to the ring traveler. The ring should have low wear, since, with increasing wear of the ring, the smooth running of the ring traveler on the ring is also impaired, and this may lead to increased thread breaks. Moreover, with increasing wear defects of the ring, the wear of the ring traveler also increases, thus leading to shorter service lives of the ring traveler and ring, and this, in turn, and also the increased thread breaks, raise the production costs.
U.S. Pat. No. 2,970,425 discloses rings for ring spinning and ring twisting machines, having a polished core which is electrolytically coated with nickel, chrome or other conventionally obtainable metals, this coating, in turn, being polished.
The object of the present invention is, therefore, to provide a ring for ring spinning and ring, twisting machines, which allows a more economical use of rings and rings travelers.
This object is achieved by means of a ring which has the feature of claim 1.
By means of a hard chrome layer, the ring acquires very hard wear-resistant surface which is applied preferably directly to a core of the ring, the ring acquires a very hard wear-resistant surface which adheres firmly to the core of the ring. Hardness values of the hard chrome layer, as measured according to Vickers HV 0.05, of 900 to 1300, preferably with values of more than 1000, are advantageous. Surprisingly, the hard chrome layer can be used without difficulty as a coating for the ring, even though very high temperatures {up to about 1000xc2x0 C.) may occur during the rapid rotation of the ring travelers on the ring. A person skilled in the art knows (cf. Schatt: xe2x80x9cWerkstoffe des Maschinen-, Anlagen- und Apparatebauesxe2x80x9d [xe2x80x9cMaterials in mechanical engineering, plant construction and apparatus engineeringxe2x80x9d], VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig 1982, page 144) that hard chrome layers soften at temperatures above 400xc2x0 C., which is why the use of hard chrome coatings has never been considered hitherto for rings. The core of the ring has a core surface which has been polished before the application of the hard chrome layer. The core is coated with a copper or nickel layer which is then, in turn, polished and on which the hard chrome layer is arranged. Particularly advantageously, such nickel or copper layers are on the core and under the hard chrome layer under corrosive conditions of use of the ring. A hard chrome layer applied to a polished core surface has a very smooth surface, thus giving rise to a very smooth run of a ring traveler on the ring hard-chrome plated in this way. Commissioning, without the ring being run in, is therefore possible without any problems, thus greatly reducing the production loss due to running-in times.
Rings having a core with a nickel or copper layer which is arranged under the hard chrome layer have particularly suitable for use under extreme conditions, such as, for example, wet spinning.
A ring, of which the hard chrome layer applied to the core of the ring likewise has a polished surface, affords special advantages, since, due to the polishing of the surface of the hard chrome layer, sharp-edged points of chrome crystals which may project from the surface of the hard chrome layer are rounded. These pointed sharp-edged crystals of the hard chrome layer act in the manner of a tile and lead to pronounced wear in objects sliding or slipping over the hard chrome layer. These file-like properties of the hard chrome layers known hitherto are another reason why hard chrome layers have never been considered hitherto for rings for ring spinning or ring twisting machines. However, if the hard crystal points of the hard chrome layer are rounded by polishing, this problem is eliminated. The ring still opposes only slight running resistance to the ring traveler rotating on it and there is no increased wear on the ring traveler. If, therefore, the core surface and the surface of the hard chrome layer are polished, a very smooth, hard and wear-resistant ring surface is obtained, on which the ring traveler can rotate with only slight wear. At the same time, before the hard chrome layer is applied, the roughness of the core 10 surface amounts, for example, to Ra 0-0.3 pm, preferably below 0.2 pm. At an Ra value of the core surface of, for example, 0.15 pm, the surface of the hard chrome layer applied to it also has a roughness of approximately 0.15 pm.
When structured hard chrome layers (so-called Topocrom layers) and/or chrome dispersion layers, which are enriched with nonmetallic components (ECD layers) are used, the properties of the hard chrome layer can be varied and can be adapted exactly to the respective requirements.
It is likewise advantageous if the core of the ring is composed of heat-treated steel. The high speeds at which the ring travelers rotate on the rings may give rise to high centrifugal forces, so that the ring travelers load the ring with corresponding pressure forces. Thread breaks at these rotational speeds may lead to a sudden impact load on the ring by the ring traveler. Too soft a basic material of the core leads to damage to the core and to the hard chrome layer in the event of such pressure or impact loads. By contrast, if the basic material of the ring is a heat-treated steel, the material lying under the hard chrome layer does not yield, even under high pressure load and sudden impact load, and the ring can survive these loads, even without the hard chrome layer and the core lying under it being damaged. This is possible because coating with the hard chrome layer takes place at temperatures of below 100xc2x0 C. and, as a result, the properties, such as, for example, the hardness, of the basic material are no longer modified, for example, by recrystallization or heat diffusion processes. The service life of the ring is increased, and, even after an event, such as, for example, a thread break, it continues to be possible for the ring traveler to run smoothly, with low wear, on the ring. Heat-treated rolling-bearing steel has proved particularly suitable for use as the core of a ring.
The hard chrome layer advantageously has a thickness of between 1 pm and 60 pm, in a preferred embodiment the layer thickness being greatest in the region of the highest stress, that is to say in those regions of the ring which come into contact with the ring traveler while it is running on the ring.
A ring having the hard chrome layer only in the regions which form contact surfaces between ring and ring traveler when the ring traveler is running on the ring leads, in the same way as a ring coated completely with a hard chrome layer, to better running properties of the ring traveler on the ring and therefore to longer service lives, to fewer thread breaks and also to lower wear on the ring itself, as a result of which, by means of such a ring, a more economical use of the ring and ring traveler is also possible.
The ring has at least one electrocontact location, via which the ring is supplied with current during the application of the hard chrome layer. This electrocontact location is advantageously situated in the region of a seat which is located opposite the region, for example, a flange, having the contact surfaces. This arrangement ensures that no undesirable unevennesses, roughnesses or other disturbances occur in the region of the contact surfaces due to the electrocontact locations in the hard chrome layer or on the surface of the ring. Even when the position of the electrocontact locations can no longer be located by the naked eye after the polishing of the hard chrome layer, the hard chrome layer may nevertheless have in these places microdisturbances which have an adverse effect on the wearing resistance or running of the ring traveler or the wearing resistance of the ring.
A hard-chrome plated ring according to the invention may advantageously be used in all spinning mills and twisting mills which operate with ring spinning and ring twisting machines respectively, since the production costs can be lowered, using such a ring. The ring affords special advantages wherever materials are processed which, during processing, discharge lubricating substances, such as, for example, animal fat or fibers with lubricating properties, in the region of the ring and of the ring traveler. The ring is very particularly suitable for the processing of cotton with its short fibers which have a lubricating action. Since the surface of the ring has very high wear resistance and opposes only slight running resistance to the ring traveler, so that the latter runs with very low wear on such a ring, there is no need for any additional lubrication, such as, for example, with molybdenum disulfide lubricant, in order to ensure long service lives and continuous operation with few thread breaks. The ring is highly suitable even for extreme conditions such as occur during wet spinning. Good corrosion resistance, as is particularly important under these conditions, is achieved by means of a ring traveler, the hard chrome layer of which has, for example, a nickel-plated undercoat or copper-plated undercoat. Further preferred embodiments and uses are a subject matter of further dependent claims.